APOLLO SPACECRAFT PROPULSION SYSTEMS DESIGN PHILOSOPHIES

Abstract

The Apollo era was a remarkable time for manned spacecraft. In order to set our sights on once again leaving low earth orbit, it is a worthwhile exercise to take a look back at the engineering successes of Apollo, the overarching design philosophies behind the engineering and program decisions, and the lessons they learned that can be applied to current and future space programs. One project performed at The Johns Hopkins University's Chemical Propulsion Information Analysis Center (CPIAC) was to screen extensive amounts of design documentation and reports from multiple sources to identify, analyze, cross reference, and distill information on the underlying philosophy behind design decisions for the Apollo spacecraft's propulsion systems. This paper will highlight some of the key findings from that research, focusing on the design philosophies and factors that contributed to Apollo’s success. A discussion of the design philosophies and lessons learned from the design of Mercury, Gemini, and Apollo propulsion systems is provided. The lessons learned from Project Mercury were applied to the design of the Gemini systems. The purpose of the Gemini project was to provide direct support to the lunar effort by testing concepts and exploring system technologies for use in the Apollo program. Thus, the Apollo project represented an effort largely based on two successful manned spaceflight programs. The primary program approach factors and lessons learned from the Gemini and Mercury programs that contributed to the reliability and success of the Apollo design are discussed. The design philosophy and how each factor contributed to the success of the Apollo program is discussed. I. Introduction HE Mercury program had the goal of launching a man into space and returning him safely, with the side goal of seeing what a person would be capable of doing while in the space environment. At the time, it was unknown if the human body could even function in space, so the spacecraft’s re-entry control system was fully automated, with the manual system being secondary for experimental manned control purposes. The systems in the Mercury capsule (figure 1) were stacked one on top of the other within the capsule, not allowing for a component replacement or any other repair to be performed without having a direct affect on numerous other systems. The Gemini capsule (figure 2) was initially intended to be just a larger version of the Mercury capsule with some of the design problems corrected based on the lessons learned. But the Gemini’s program was meant to be used as a test of the requirements and capabilities that were needed to go to the Moon. Gemini mission requirements of testing the docking, rendezvous, and various other capabilities necessary for the Apollo program’s lunar mission required the addition of an orbit adjust and maneuvering system. The Gemini flight and experiment data was used for determining the requirements for Apollo systems. The lessons learned from the Mercury and Gemini programs were applied in principle to the Apollo spacecraft propulsion systems, as well to the Apollo program as a whole. This resulted in Apollo attaining the required reliability through design redundancy; extensive development, qualification, and acceptance testing; and stringent quality assurance for both development and production hardware.